A telephone call is originated by transmitting digits, identifying a destination, to a telephone exchange. If the destination is not part of the local exchange, the call must be routed to another destination exchange, sometimes via a network of exchanges, also called nodes. Various routes may be possible between an originating node and a terminating node. An exchange generally contains data defining first choice and alternate paths for different destinations, as defined by an area code, and/or country code, and exchange code digits. Inter-exchange transmission facilities may consist of several circuit groups, each having a plurality of circuits, also referred to as trunks. A problem in telecommunication networks is the control of traffic flow to avoid congestion which may be caused by equipment faults or changes in call activity. Some changes in call activity can be anticipated, for example, activity levels during business hours. Other call activity may be the result of a natural disaster or other event which increases traffic in a certain area manyfold.
Prior art traffic management is predicated on traffic measurements taken at each of the circuit groups in an exchange. In the prior art, off-line systems are used to collect the activity data of the various circuit groups and the data is analyzed in order to determine the activity of a group of circuits between two exchanges in order to define overloaded routes or route with low call completion rates. Network management entails the control of a multi-node network by restricting traffic on certain routes and allowing traffic on other routes in order to prevent undue congestion. A problem of the prior art is that the control information is not available in real-time and in some cases the need for traffic rearrangement no longer exists by the time the computations have been made. Furthermore, in a system where preferred and alternate routes are allowed, a particular circuit group being analyzed may carry direct traffic from an exchange to a next exchange and alternate route traffic coming from yet another exchange and routed via this exchange to the next exchange. Typically, traffic is routed via an alternate for lack of availability of a direct route to a destination. The prior art arrangement makes no provision for distinguishing between direct route and alternate route traffic on a circuit group and where a circuit group is used for a number of different alternate routes, prior art systems may create conflicting network management data. Consequently, the prior art systems require analysis by a human expert to prevent the applications of control which would be detrimental to the operation of the network.
Another problem of the prior art is that while congestion can be detected by measurements, for example, such as those indicating incompleted calls on a circuit group and traffic can be diverted from that circuit group to another, there is no convenient way of determining when a circuit group will be ready to resume normal traffic handling. A congestion typically is due to a problem at the next node in the network or at a subsequent location. Short of periodically releasing a circuit to which management control has been applied and later analyzing if additional congestion has resulted, there is no convenient way of restoring a circuit to its normal traffic handling capacity.